These treatment devices are notably known as a device for heat treatment of a reactive medium, where by <<heat treatment>> are meant various treatments carried out by heating such as evaporation, drying, roasting, extraction of natural products in suspension in a solvent to radiation, reaction or chemical synthesis with heating by dielectric losses (with view of analyzing or producing chemical compounds), dehydration, baking, discoloration, polymerization, cross-linking, treatments with supercritical fluids, dissociation, removal of volatile compounds, etc., as well as various treatments performed simultaneously with heating, such as mixing or milling.
For such heat treatments, it is notably known how to use electromagnetic radiations of the microwave or high frequency type. Microwave electromagnetic radiation relates to waves, the frequency of which is comprised between about 300 MHz and about 30 GHz, preferentially between 400 MHz and 10 GHz, and preferentially between 915 MHz and 2.45 GHz. High frequency electromagnetic radiation relates to waves, the frequency of which is comprised between about 100 kHz and about 300 MHz, preferentially between 13 MHz and 28 GHz.
Such treatment devices find applications for many types of reactive media, which involve a single reagent or a mixture of reagents in variable proportions, in the solid, liquid or gas state, with or without catalysts, said medium comprising at least one component sensitive to radiation. The reactive medium may be of the solid type (for example of granular or powdery type), of the gas, plasma, liquid type (with a solvent and/or solutes absorbing electromagnetic radiation).
The invention is particularly adapted to a microwave electromagnetic radiation, for reasons related to the geometry of wave guides and to numerous applications contemplated for this type of radiation.
As illustrated in FIG. 1, such a device for treating a reactive medium with electromagnetic radiation comprises:                a microwave electromagnetic radiation generator 100 like for example and in a non-limiting way a magnetron generator or a semiconductor generator;        a reactor 200 containing said reactive medium, wherein the reactor may assume the shape of a reservoir or a continuous line for circulating said reactive medium; and        a device 300 for transmitting the electromagnetic radiation generated by the generator to the reactive medium contained in said reactor 200.        
This transmission device comprises:                means 400 for transmitting electromagnetic radiation positioned at the output of the generator 100 and coupled with said reactor 200 in order to transmit the electromagnetic energy to the reactor, these transmission means being of course adapted to electromagnetic radiation and which may for example consist of a wave guide conventionally used in the field of microwaves;        coupling means 500 arranged for allowing transfer into the reactive medium of the electromagnetic energy from the wave guide 400.        adaptation means 800 designed in order to allow optimization of transfer of electromagnetic energy to the reactive medium depending on certain physico-chemical parameters of the reactive medium, or even of their time-dependent changes, such as dielectric characteristics, conductivity or polarity of the compounds such as for example the solvent, the chemical reagents, the catalysts, etc.        
When operating, the generator 100 generates electromagnetic radiation at a given frequency, for example 2,450 MHz, the wave guide 400 guides the generated electromagnetic radiation, the coupling means 500, known to one skilled in the art, ensuring the energy transfer in the reactor 200 and therefore to the reactive medium, and finally the adaptation means 800 ensure optimization of the transfer of energy to said reactive medium, notably in terms of transmitted power.
The coupling means generally comprise an application device for applying the energy to the reactive medium, currently called an energy applicator, the selection of which depends on the radiation used (high frequency and microwave radiation), on the dimensional characteristics of the medium to be treated and on its treatment mode.
For high frequency applicators, the following applicators are notably known:                capacitive applicators formed with two capacitor plates between which the high frequency voltage is applied;        inductive applicators for treating sufficiently conductive materials, these applicators consist of a solenoid energized with a high frequency current;        applicators with alternating bars for relatively planar materials consisting of tubular or bar electrodes;        applicators with alternating rings or loops for thread-like materials forming the electrodes.        
The major drawback of these applicators is that they are not very or not adapted for ensuring energy transfer into a liquid mass and homogeneously.
For microwave applicators, the following applicators are notably known:                applicators with a localized field of the single-mode cavity type;        applicators with a diffuse field of the multi-mode cavity type;        applicators with a near field of the radiating antenna guide type.        
As regards applicators with a localized field or with a diffuse field, they require a reactor at least partly consisting of a material transparent to the waves, i.e. not absorbing the waves, such as for example polytetrafluoroethylene or quartz, which is positioned inside the cavity of the applicator. The reactor containing the reactive medium is then subject to electromagnetic radiation coming from the outside.
The applicator with a localized field, of the single-mode type, is formed with a single-mode cavity of predetermined size, resonating at the emission frequency according to radiation in the direction of the waveguide. This single-mode cavity allows a relatively homogeneous distribution of the electromagnetic field inside the cavity. Nevertheless, with this type of single-mode applicator, the amount of material to be treated is limited by the dimensions of the cavity and therefore of the waveguide. For an industrial application, it is necessary to provide a complex and costly apparatus comprising several single-mode applicators placed in parallel in order to have sufficient output, as well as a complex circulation system for the reactive medium. Further, the transferable electromagnetic energy is limited by the volume at the interface between the product to be treated and the radiation.
The applicator with a diffuse field, of the multi-mode type, on the other hand provides a non-homogeneous distribution of the electromagnetic field inside the cavity, with the presence of hot points. Such a distribution limits the volume of the samples to be treated in the applicators of the multi-mode type, and furthermore requires setting into motion or stirring of the sample in order to ensure homogeneity of the heating by microwaves.
A common drawback to both of these applicators of the single-mode type or multi-mode type is that they require reactors in a suitable material in order not to absorb the waves. In addition to being particularly complex and costly to produce, these reactors transparent to the waves are limited in size and in shape, thereby limiting the treatment by waves to certain reactions and certain reactive media, and excluding other reactions where the shape and the length of the reactor may have a predominant role. It is also noted that for reactions which have to be conducted under high pressure, independently or not of the heating induced by the electromagnetic radiation, these wave-transparent reactors most often withstand high pressures with difficulty.
The other drawbacks common to both of these applicators, of the single-mode or multi-mode type, result from the difficulty of obtaining a constant electric field in the reactor, and finally from the fact that the geometry of the cavity depends on the radiation frequency so that an applicator with a localized field can only operate at a given single frequency.
As regards the applicators with a near field, they are known from the prior art notably from European patent application No. EP 0 329 338 which discloses a device for treating by microwaves ceramic powders in a high pressure environment where the near field applicator is made as a radiating antenna. This device includes a reactor forming a high pressure resonant cavity, in the interior of which microwave radiation is introduced by a rectilinear antenna which partly extends into the cavity.
Patent application FR 08/01541 filed by the applicant also describes a near field type applicator which at least partly extends into the interior of the reactor, the reactor forming a resonant cavity inside which the electromagnetic radiation is introduced by the applicator. In this document, the applicator comprises at least one lossy transmission line having an interface for transferring electromagnetic energy towards the reactive medium.
Near field type applicators solve part of the drawbacks of the applicators of the single-mode or multi-mode type, notably because they allow the radiation to be directly transmitted towards the interior of a reactor, thereby avoiding the use of a reactor transparent to the waves with all the constraints mentioned above.
The adaptation means 800 comprise in a known way:                a short-circuit piston 810 comprising a metal plate, in copper or aluminium for example, placed perpendicularly to the axis of the wave guide 400, said short-circuit piston 810 is positioned at the end 490 of the wave guide 400 opposite to the generator 100, and therefore downstream from the reactor 200, in order to impose a boundary condition for a stationary wave to be present in the wave guide 400;        a variable coupling iris 820, positioned in the wave guide 400 between the generator 100 and the short-circuit piston 810, and more particularly upstream from the reactor 200.        
In a known way, the short-circuit piston 810 and the coupling iris 820 are both translationally mobile inside the wave guide 400, in order to obtain a resonant cavity of adjustable length in the wave guide 400, and to thus adapt and optimize transmission of electromagnetic energy to the reactive medium. Further, the short-circuit piston 810 and the coupling iris 820 are positioned relatively to the reactor 200 in order to allow centering of the stationary wave on the reactor 200, i.e. the positioning of an antinode of the stationary wave, corresponding to a maximum amplitude, at the reactor 200.
As illustrated in FIG. 1, the treatment devices of the state of the art consist of elements aligned one after the other, i.e. the wave generator 100, the coupling iris 820, the chemical reactor 200, the coupling means 500 and the short-circuit piston 810 are located in the same alignment, along a linear wave guide 400. In such a configuration, the transmission device 300 is said to be in line, with a linear wave guide 400 and aligned adaptation means 800: the coupling iris 820 and the short-circuit piston 810 are positioned on either side of the means 500 for coupling with said reactor 2.
Such an arrangement in line has certain drawbacks, notably for implanting means for driving the short-circuit piston 810 and the coupling iris 820 along the wave guide 400. Indeed, this arrangement in line imposes the use of two distinct servo-motors, a first M1 and a second M2 motor respectively, for driving in translation the short-circuit piston 810 and the coupling iris 820 respectively; both of these motors M1, M2 being synchronized by means of a device (not shown) for controlling the motors M1 and M2. The use of two motors M1, M2 thus increases the cost of such a transmission device because of the two motors M1, M2 and of the control device for synchronizing these motors. Further, these motors increase congestion around the wave guide and may furthermore limit access to the reactor 2 or to the coupling means 500, which is particularly redhibitory with a reactor which operates continuously. These motors may thus cause an annoyance to the operators who are working on the device, notably for operators who wish to access the reactor in order to replace it, introduce products or extract products for the purpose of analyses.
The use of a single motor cannot be contemplated for such line transmission devices. Indeed, this would require the use of translational coupling mechanical means between said single motor and the two mobile members of the adaptation means 800 (short-circuit piston 810 and coupling iris 820), said mechanical translational coupling means for example assuming the shape of connecting rods which would circulate along the wave guide 400 on either side of the reactor 200. Such translational coupling means are of course unacceptable for such a device since they form parts external to the wave guide, circulating along the wave guide, and they may be a nuisance to the operators working along the wave guide, and more particularly on the reactor 200. Further, the short-circuit piston 810 and the coupling iris 820 may be very spaced out, sometimes by several meters, so that the coupling means have to extend over a long distance, which may be detrimental to the coupling accuracy between the short-circuit piston 810 and the coupling iris 820.
Another drawback of these line transmission devices is that in order to meet safety standards notably in effect in chemistry laboratories, provision of a long transmission line is known in order to move the wave generator 100 away from the reactor 200, and to thereby isolate it at a certain distance, with possible interposition of a concrete wall. This separation or moving away of the generator 100 has the purpose of providing protection against any risk of fire or explosion, in particular when the reactor 200 contains solvents or other volatile materials and capable of catching fire or even causing an explosion when they are in contact with a spark generated at the generator 100, and more particularly at the power supply of the generator. For example, it is noted that a magnetron requires a high voltage power supply of the order of 12-15 kV. In order to avoid the occurrence of these electric flash phenomena in wave guides, it is also known how to provide inertization of wave guides by filling them up with a neutral gas such as nitrogen.
Further, it should be noted that such a separation distance is suitable for preventing the generator and its power supply from being subject to chemical aggressions by products contained in the reactor 200, notably during their introduction into the reactor 200.
However, such a separation distance has the consequence that the transmission device with a suitable length is particularly costly and cumbersome since it requires a great length inside the room which receives the latter, or even requires two adjacent rooms. This linear congestion may also cause annoyance for an operator working on this device, since it may be difficult to walk around the device in order to carry out adjustments on its various elements.
The state of the art may also be illustrated by the teaching of documents DE 28 22 370 A1, WO 01/11952 A and US 2007/131678. Document DE 28 22 370 A1 describes a microwave treatment device comprising a wave guide transmitting the microwave radiation of a generator to material droplets which are directly introduced into the wave guide by means of a droplet dispenser, wherein the wave guide includes a curved segment in a general “U” shape. Documents WO 01/11925 A and US 2007/131678 describe treatment devices comprising an electromagnetic radiation transmission device comprising a wave guide transmitting the radiation from a generator to a reactive medium circulating on a conveyance path directly extending inside the wave guide, wherein the wave guide includes a curved segment in a general “U” shape. The devices described in these three documents are of the localized field applicator type, of the single-mode type, wherein the interior of the wave guide forms the single-mode cavity with all the drawbacks mentioned above.